1. Field of the Invention
This invention pertains to torches and in particular to automatic torches used in the Air-Carbon Arc Cutting and Gouging Process. In the Air-Carbon Arc Cutting and Gouging Process an electrode is used to strike and maintain an arc between a workpiece causing melting of metal underneath the arc. As melting progresses a stream of high pressure air directed along the electrode to the arc causes the molten metal to be forcibly removed from the influence of the arc, thus leaving a groove or gouge, in the surface of the workpiece. The process can be also used to cut completely through the workpiece in the area traversed by the electrode and the arc. Torches for use in the Air-Carbon Arc Cutting and Gouging Process include an automatic torch wherein the torch is mounted on a carriage or other device for movement along on a predetermined path. Automatic torches include means to feed electrodes toward the workpiece at a rate selected to match consumption of the electrode by the electric arc. Most automatic torches include provision for using jointed electrodes so that successive electrodes (lengths) can be mated to, in effect, provide a continuous electrode of indeterminate length.
2. The Prior Art
One type of automatic Air-Carbon Arc Cutting and Gouging Torch is disclosed in U.S. Pat. No. 3,317,779. In this patent rollers are used to frictionally engage the electrode and feed it through a nozzle containing a contact shoe which conducts electricity to the electrode. The nozzle has provision for directing air along the electrode to the arc. The patent includes means for pivoting the housing supporting drive rolls having a fixed position relative to each other about an axis to, in effect, change the spacing between the rollers and increase frictional contact with the electrode.
Means for controlling the torch including the spacing of the torch to the workpiece and the feeding of the electrode are disclosed in U.S. Pat. No. 3,659,071. The '071 patent is an improved version of an automatic torch and control system.
Jointed electrodes for use in automatic torches are disclosed in U.S. Pat. No. 3,131,290.
Lastly, the current state of the art is reflected in the Model N Automatic Air-Carbon Arc Cutting and Gouging Torch manufactured and sold by the Arcair Company of Lancaster, Ohio.
One of the problems with prior art automatic torches is compensating for electrodes that are not perfectly straight, electrodes that vary in diameter for a given nominal size, and poor joint fit of successive lengths of electrode.